I doubt you can tell the difference between a V0 rip, 320kbps MP3 and a flac. Even youtube audio can be decent if it's a recently uploaded video with an okay source format - they use a reasonably high bitrate Opus if memory serves.

But yeah, classic 128 kbps mp3s are garbage. I also prefer FLAC if only for archival purposes so it can be transcoded to the "latest and greatest" codec. :P

If he has enough experience, then he probably can. Much like users can tell difference between 120 and 60fps or 144 and 120fps. A trained mind can do it.

MP3 lost all value to me when the age of clipping came in due to the battle of loudness in audio music. Metallica being a terrible culprit of the process.